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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::regex_traits&lt;CharT&gt;::</span>lookup_classname</h1>
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../regex_match.html" title="cpp/regex/regex match"><span class="t-lines"><span>regex_match</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../syntax_option_type.html" title="cpp/regex/syntax option type"><span class="t-lines"><span>syntax_option_type</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
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</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../regex_traits.html" title="cpp/regex/regex traits"><tt>std::regex_traits</tt></a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="">
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="regex_traits.html" title="cpp/regex/regex traits/regex traits"><span class="t-lines"><span>regex_traits::regex_traits</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="length.html" title="cpp/regex/regex traits/length"><span class="t-lines"><span>regex_traits::length</span></span></a></div></div></td></tr>
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="translate_nocase.html" title="cpp/regex/regex traits/translate nocase"><span class="t-lines"><span>regex_traits::translate_nocase</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="transform.html" title="cpp/regex/regex traits/transform"><span class="t-lines"><span>regex_traits::transform</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="transform_primary.html" title="cpp/regex/regex traits/transform primary"><span class="t-lines"><span>regex_traits::transform_primary</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lookup_collatename.html" title="cpp/regex/regex traits/lookup collatename"><span class="t-lines"><span>regex_traits::lookup_collatename</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><strong class="selflink"><span class="t-lines"><span>regex_traits::lookup_classname</span></span></strong></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="isctype.html" title="cpp/regex/regex traits/isctype"><span class="t-lines"><span>regex_traits::isctype</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="value.html" title="cpp/regex/regex traits/value"><span class="t-lines"><span>regex_traits::value</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="imbue.html" title="cpp/regex/regex traits/imbue"><span class="t-lines"><span>regex_traits::imbue</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="getloc.html" title="cpp/regex/regex traits/getloc"><span class="t-lines"><span>regex_traits::getloc</span></span></a></div></div></td></tr>
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<table class="t-dcl-begin"><tbody>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> ForwardIt <span class="sy1">&gt;</span><br>
<p>char_class_type lookup_classname<span class="br0">(</span> ForwardIt first,<br>
                                  ForwardIt last,<br>
</p>
                                  <span class="kw4">bool</span> icase <span class="sy1">=</span> <span class="kw2">false</span> <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div></td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
</tbody></table>
<p>若字符序列 <code>[first, last)</code> 表示当前感染的 locale 中合法的字符类名称（即正则表达式中 <code>[:</code> 与 <code>:]</code> 之间的字符串），则返回表示此字符类的实现定义值。否则，返回零。
</p><p>若参数 <code>icase</code> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，则字符类忽略字符大小写，例如带 <span class="t-lc"><a href="../syntax_option_type.html" title="cpp/regex/syntax option type">std::regex_constants::icase</a></span> 的正则表达式 <code>[:lower:]</code> 生成以 <code>[first, last)</code> 指示字符串 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"lower"</span></span></span> ，且 <span class="t-c"><span class="mw-geshi cpp source-cpp">icase <span class="sy1">==</span> <span class="kw2">true</span></span></span> 的 <code>regex_traits&lt;&gt;::lookup_classname()</code> 调用。此调用返回与带 <span class="t-c"><span class="mw-geshi cpp source-cpp">icase <span class="sy1">==</span> <span class="kw2">false</span></span></span> 的正则表达式 <code>[:alpha:]</code> 所生成者相同位掩码。
</p><p>始终以窄和宽字符形式辨认下列字符类，并返回如下的，感染的 locale 的 <span class="t-lc"><a href="../../locale/ctype.html" title="cpp/locale/ctype">std::ctype</a></span> 平面所获得的匹配分类所对应的分类（有 <span class="t-c"><span class="mw-geshi cpp source-cpp">icase <span class="sy1">==</span> <span class="kw2">false</span></span></span> ）：
</p>
<table class="t-dsc-begin">

<tr class="t-dsc-sep">
<td colspan="2">  
</td></tr>
<tr class="t-dsc-hitem">
<td> 字符类
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype.html" title="cpp/locale/ctype">std::ctype</a></span> 分类
</td></tr>


<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"alnum"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::alnum</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"alpha"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::alpha</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"blank"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::blank</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"cntrl"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::cntrl</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"digit"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::digit</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"graph"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::graph</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"lower"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::lower</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"print"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::print</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"punct"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::punct</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"space"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::space</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"upper"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::upper</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"xdigit"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::xdigit</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"d"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::digit</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"s"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::space</a></span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"w"</span></span></span>
</td>
<td>  <span class="t-lc"><a href="../../locale/ctype_base.html" title="cpp/locale/ctype base">std::ctype_base::alnum</a></span> 可选地加上带 '_'
</td></tr>
</table>
<p>对字符串 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"w"</span></span></span> 返回的分类可以准确地与 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">"alnum"</span></span></span> 相同，该情况下 <span class="t-lc"><a href="isctype.html" title="cpp/regex/regex traits/isctype">isctype()</a></span> 显式加上 '_' 。
</p><p>系统提供的本地环境可提供额外分类，如 <span class="t-lc">"jdigit"</span> 或 <span class="t-lc">"jkanji"</span> （该情况下它们亦可通过 <span class="t-lc"><a href="../../string/wide/wctype.html" title="cpp/string/wide/wctype">std::wctype</a></span> 访问）。
</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
<table class="t-par-begin">


<tr class="t-par">
<td>  first, last
</td>
<td> -
</td>
<td> 一对迭代器，确定表示字符类名的字符序列
</td></tr>
<tr class="t-par">
<td>  icase
</td>
<td> -
</td>
<td> 若为 true ，则忽略字符分类中的大小写区别
</td></tr>
<tr class="t-par-hitem">
<td colspan="3"> 类型要求
</td></tr>
<tr class="t-par-req">
<td colspan="3"> -<div class="spacer"></div><code>ForwardIt</code> 必须满足<a href="../../named_req/ForwardIterator.html" title="cpp/named req/ForwardIterator"><i>遗留向前迭代器</i> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyForwardIterator)</span> </a> 的要求。
</td></tr></table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
<p>以给定的字符类确定的表示字符分类的位掩码，或若类未知则为 <code>char_class_type()</code> 。
</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
<div class="t-example"><p>演示定制 regex_traits 的 lookup_classname/isctype 实现</p><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">运行此代码</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;locale&gt;</span>
<span class="co2">#include &lt;regex&gt;</span>
<span class="co2">#include &lt;cwctype&gt;</span>
 
<span class="co1">// 此定制正则表达式特性以 wctype/iswctype 实现 lookup_classname/isctype</span>
<span class="kw1">struct</span> wctype_traits <span class="sy4">:</span> <a href="../regex_traits.html"><span class="kw2026">std::<span class="me2">regex_traits</span></span></a><span class="sy1">&lt;</span><span class="kw4">wchar_t</span><span class="sy1">&gt;</span>
<span class="br0">{</span>
    <span class="kw1">using</span> char_class_type <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">wctype_t</span><span class="sy4">;</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> It<span class="sy1">&gt;</span>
    char_class_type lookup_classname<span class="br0">(</span>It first, It last, <span class="kw4">bool</span><span class="sy1">=</span><span class="kw2">false</span><span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
        <span class="kw1">return</span> <a href="../../string/wide/wctype.html"><span class="kw1193">std::<span class="me2">wctype</span></span></a><span class="br0">(</span><a href="../../string/basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">(</span>first, last<span class="br0">)</span>.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
    <span class="br0">}</span>
    <span class="kw4">bool</span> isctype<span class="br0">(</span><span class="kw4">wchar_t</span> c, char_class_type f<span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
        <span class="kw1">return</span> <a href="../../string/wide/iswctype.html"><span class="kw1192">std::<span class="me2">iswctype</span></span></a><span class="br0">(</span>c, f<span class="br0">)</span><span class="sy4">;</span>
    <span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    std<span class="sy4">::</span><span class="me2">locale</span><span class="sy4">::</span><span class="me2">global</span><span class="br0">(</span><a href="../../locale/locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"ja_JP.utf8"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../../io/cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a>.<span class="me1">sync_with_stdio</span><span class="br0">(</span><span class="kw2">false</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../../io/cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a>.<span class="me1">imbue</span><span class="br0">(</span><a href="../../locale/locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
 
    <a href="../match_results.html"><span class="kw2011">std::<span class="me2">wsmatch</span></span></a> m<span class="sy4">;</span>
    <a href="../../string/basic_string.html"><span class="kw1232">std::<span class="me2">wstring</span></span></a> in <span class="sy1">=</span> L<span class="st0">"けものフレンズ"</span><span class="sy4">;</span>
    <span class="co1">// 匹配所有字符（它们被分类为 alnum ）</span>
    <a href="../regex_search.html"><span class="kw2013">std::<span class="me2">regex_search</span></span></a><span class="br0">(</span>in, m, <a href="http://zh.cppreference.com/w/cpp/regex/basic_regex"><span class="kw2001">std::<span class="me2">wregex</span></span></a><span class="br0">(</span>L<span class="st0">"([[:alnum:]]+)"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../../io/cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"alnums: "</span> <span class="sy1">&lt;&lt;</span> m<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// 打印 "けものフレンズ"</span>
    <span class="co1">// 只匹配片假名</span>
    <a href="../regex_search.html"><span class="kw2013">std::<span class="me2">regex_search</span></span></a><span class="br0">(</span>in, m,
                      <a href="http://zh.cppreference.com/w/cpp/regex/basic_regex"><span class="kw1999">std::<span class="me2">basic_regex</span></span></a><span class="sy1">&lt;</span><span class="kw4">wchar_t</span>, wctype_traits<span class="sy1">&gt;</span><span class="br0">(</span>L<span class="st0">"([[:jkata:]]+)"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../../io/cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"katakana: "</span> <span class="sy1">&lt;&lt;</span> m<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// 打印 "フレンズ"</span>
<span class="br0">}</span></pre></div></div>
<p>输出：
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">alnums: けものフレンズ
katakana: フレンズ</pre></div></div> 
</div>
<p><br>
</p>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="isctype.html" title="cpp/regex/regex traits/isctype"> <span class="t-lines"><span>isctype</span></span></a></div></div>
</td>
<td>  指示字符类中的成员关系指示 <br> <span class="t-mark">(公开成员函数)</span>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../../string/wide/wctype.html" title="cpp/string/wide/wctype"> <span class="t-lines"><span>wctype</span></span></a></div></div>
</td>
<td>  在当前 C 本地环境中查找字符分类类别 <br> <span class="t-mark">(函数)</span> </td></tr>
</table>

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